actuators (1)

8/3/2019 Actuators (1)

1/13

RR

ActuatorsActuators

Instructor: Dr. Hong Zhang

Mechanical Engineering

Rowan University

ME ROWANME ROWAN 22

RR Homework 1Homework 1

Chapter 2:

Problem 1, 10, 14, 17, 18

Chapter 3:

Problem 9

Due: March 2, 2004

ME ROWANME ROWAN 33

RR ActuatorsActuators

Actuators are the elements that transformthe control inputs to actions of a machine.

The common types of actuators:

Electric motors

DC & AC motors

Stepper motors

Servo motors

Hydraulic & Pneumatic actuators

Shape memory metal actuators

Others

ME ROWANME ROWAN 44

RR Mechanical Actuation SystemsMechanical Actuation Systems

Mechanisms: Devices that transform motionfrom one form to some other required form.

Mechanical elements: Linkage, cam, gear,rack-and-pinion, chain, belt drive, etc.

Functions:

Force amplification

Change of speed

Transfer rotation between axis Others

ME ROWANME ROWAN 55

RR Four Bar LinkFour Bar Link

1

4

3

2

1

4 3

2

14 3

2

Double-lever

2143 llll +>+ 2143 llll +


2/13

ME ROWANME ROWAN 77

RR Gear TrainGear Train

A

B

B

A

n

n=

C

D

A

B

C

D

A

B

D

A

n

n

n

n

n

n

n

n=

=

A C DB

A B

ME ROWANME ROWAN 88

RR Planetary Gear TrainPlanetary Gear Train

SunRing Gear

Planet

Arm

armF

arm

gearsdrivenonteethofnumberofproduct

gearsdriveronteethofnumberofproduct

= L

ME ROWANME ROWAN 99

RR

The sun has 40 teeth, the planet 20 teeth,and the ring gear 80 teeth. The arm is inputand the sun is output. The ring gear is heldstationary. Find the train ratio of sun/arm.

ratio of sun/arm =3

ME ROWANME ROWAN 1010

RR

Build a remotely controlled mouse:

Basic parts: a mouse set & a joystick set

Other material: anything you can buy within the limit ofthe allowance (which you can keep it as secret), andanything you find from machine shop and other places(which you need to inform the entire class and getapproval).

Tool: machines and tools available in machine shop

and electric lab, you can also use your own tool Allowance: $10 (dept.) + $10 (self), keep receipts for

peer examination prior competition

Project 1: Mouse HouseProject 1: Mouse House


RR

Date: March 10, 2004

Mouse soccer tournament Time: 5 minutes each game for 3 games

You can design and install any ball handling tool

Sumouse triangle: Time: 2 minutes

Push or trick the others out of the boundary.

Point = 10 # of stepping out down time (every 5s)

You can add any attachment to enhance your chance

CompetitionCompetition


RR Characteristics of ActuatorsCharacteristics of Actuators

Weight

Power-to-weight ratio

Stiffness: The resistance of a materialagainst deformation.

Stiff vs.Compliant

Accuracy vs. Flexibility

Reduction gears

Reduce speed, increase torque

Increased cost, number of parts, backlash, etc.


3/13


RR Bucket ScienceBucket Science

You have a 5L and a 3L bucket and unlimitedsupply of water. How to use these twobuckets to measure any amount of water

from 1L to 8L.

5L 3L


RR Hydraulic ActuatorsHydraulic Actuators

High power- to- weight ratio (depending on whetherthe pump & reservoir are included)

Large forces at low speeds (linear or rotary)

Compatible with microprocessor and electronic

control No reduction gears required

Tolerance of extreme hazardous environments

May leak

Expensive and noisy, requires maintenance

Depends on the properties of oil (dirt, temp., etc)


RR ApplicationsApplications

Dump Truck

Car Brakes

Shovel


RR Principle of Hydraulic SystemsPrinciple of Hydraulic Systems

F F

Oil

Pistons have equal areasF F

Oil

Pistons with different areas

F=F

21

'

A

F

A

F=

FA

AF

1

2'=

A1 A2


RR Common ComponentsCommon Components

Power source

Hydraulic linear or rotary cylinders and rams

Hydraulic switches and other controllers

Connecting hoses

Safety valves and other mechanisms

Sensors


RR Schematic of a Hydraulic SystemSchematic of a Hydraulic System

Sensors Controller

HydraulicPowerSource

Switch

Return

Source


4/13


RR Power SourcePower Source

Reservoir

Hydraulic pump operated by a motor or an

engine Cooling system (for pneumatic system)


RR Power SourcePower Source

Return

Oil Reservoir

Pump

Motor

None-return

valve

Pressure

relieve valveAccumulator

To system


RR Hydraulic CylindersHydraulic Cylinders

Hydraulic cylinder

Telescope cylinderSchematic drawing


RR Directional Control ValvesDirectional Control Valves

Port 1Port 3 Port 2

Spool

Port 3 Port 1Port 2

One-way valve


RR Valve SymbolsValve Symbols

Flow path Flow shut-off InitialConditions

Push-buttonSpring-button

RollerSolenoid Pneumatic Lever Pedal


RR Example: Poppet ValveExample: Poppet Valve

Poppet valve

2 port 2 position (2/2) poppet valve


5/13


RR More ExamplesMore Examples

3/2 valve 4/2 valve

Lift system

Vent

Pressure supply


RR 22--Actuator Sequential OperationActuator Sequential Operation

5

6

7

b+b-Cylinder BLimit switches

a-

a+

Start1

4

3

2

a+a-Cylinder ALimit switches

b-b+


RR Brain SugarBrain Sugar

Use 1, 5, 6, 7 and any combination of +, -, *and / to obtain 24 and 21.

2465*)17( =

21)7/51/(6 =


RR Electric MotorsElectric Motors

Most popular motor

Types:

DC motor

AC motor

Brushless motor

Step motor

Servo motor

Linear motor

Applications:


RR Basic Principles of Electromagnetic MotorsBasic Principles of Electromagnetic Motors

N

S

B

1. A magnetic field B is generated by a pair of magnets.

2. A conductor with no current will not disturb the field B.

x

3. When a conductor carries an electrical current, aconcentric magnetic field is produced along theconductors length.

4. Combined action between the two magnetic fieldscreate a mutual repulsive force forcing thewire downwards.

F

x B

BilFrr

=


RR

When there is a loop of conductor carrying current inthe magnetic field, a torque will be generated.

Electromagnetic MotorElectromagnetic Motor

Current

N S

B

F

F


6/13


RR Brushes and CommutatorBrushes and Commutator

For continuous operation, a pair of brushes andcommutator are used to change the direction of current


RR Direction Changing w/ BrushesDirection Changing w/ Brushes

(a) (b)Armature


RR A Simple MotorA Simple Motor


RR Inside a DC MotorInside a DC Motor

Field magnet

DC motor

Armature

Commutator

ContactBrushes


RR DiscussionDiscussion

How does this worlds simplest motor work?

How to reverse the direction of rotation?


RR Field CoilsField Coils

Practical motors have several loops on anarmature to provide a more uniform torqueand the magnetic field is produced by anelectromagnet arrangement called the fieldcoils.


7/13


RR Arrangement of Field CoilsArrangement of Field Coils

Field coil

Armature coil

Series wound motor

Field coil

Armaturecoil

Shunt wound motor

Field coil

Armaturecoil

Field coil

Compound motor

Armaturecoil

Field coil

Separately wound motor


RR Torque with Permanent MagnetTorque with Permanent Magnet

Force generated by oneconductor

BilF=

i

B

F

F

l

b

Torque generatedbBilT =

iknbBliT t ==

Total torque


RR Torque with Field CoilTorque with Field Coil

For motor with field coil, we just need tochangeB toKfIstator.

ikliIbKnT tstatorf ==


RR Back ElectroBack Electro--Magnetic FieldMagnetic Field

Rotating armature coil in magnetic field willinduce back e.m.f. vb

vb kv =

V

R L

Vb

A DC motor can be considered as anequivalent circuit

RkV

RvVi vb

=

=i


RR Torque and SpeedTorque and Speed

Ignoring the inductance of armature, the torque is

Where R is the armature resistance, V is theapplied voltage, and the rotational speed.

R

kVkikT vtt

)( ==

Torque

Rotational speed

V1

V2

V3


RR Torque Characteristics of a MotorTorque Characteristics of a Motor

Rotation rate (rpm)

Torque

(Nm)

10 60504030200

0.1

0.5

0.4

0.3

0.2

0.8

0.7

0.6

A 12V DC motor

A 24V DC motor

Stall

No load


8/13


RR Brain SugarBrain Sugar

Add following lines together

4100

1000

20

1030

1020

20

+) 1010


RR

Connect all 9 dots with 4 connected straight lines


RR Design ProblemDesign Problem

Known: Total mass m= 5 kg. We have 10 AA NiCd batterieswith 1.2V, 500mAh, and a DC motor with normal runningcurrent 0.15A at 12V. Suppose transmission ratio 1:10 and

stall torque of the motor is 300 oz.in.Check: 1. Whether the car can reach acceleration a=0.1g?

2. How long will the battery last?

Body

Wheel (r=4cm)

MotorBattery

Transmission


RR CalculationCalculation

Acceleration: a = 0.1 x 9.8 =0.98 m/s2

Force: F = ma = 5 x 0.981 = 4.9 N

Wheel torque:

Tw= Fr = 4.9 x 0.04 = 0.196 Nm

Minimum torque required from the motor:

Tm= Tw*10 = 1.96 Nm

= 141.61*1.96 oz.in = 278 oz.in

Stall torque of the motor is 300 oz.in300 oz.in > 278 oz.in


RR CalculationCalculation

Running power of the motor:P=VI= 12 x0.15 = 1.8 w

Running time: 500mAh = 0.5 Ah

0.5 / 0.15 = 3.3 hr

Note: You need to consider other factors inreal design, such as friction in transmission,uneven surface, etc.


RR DiodeDiode

Diode

Cathode

AnodeV

I

Forwardbiased

Reversebiased

0

Diode characteristic


9/13


RR Bipolar TransistorBipolar Transistor

BFEcIhI =

Ic Ic

Base current

Ic

Base current

Ic

Emitter

Base

Collector

NPN

Collector

Emitter

Base

PNP


RR Darlington PairsDarlington Pairs

NPN PNP

IcIc

Base current

Ic

Base current

IcIc Ic


RR H Circuit DC Motor ControllerH Circuit DC Motor Controller

V+

High

Low


RR H Circuit DC Motor ControllerH Circuit DC Motor Controller

V+

High

Low


RR MOSFETMOSFET

Drain

Source

Gate

Drain

Source

Gate

12V

12V

GND

Output portof micro-

processor

N-channel P-channel

1.High frequencyswitching

2.Easy interfacing tomicroprocessor


RR Electronic Speed ControllerElectronic Speed Controller


10/13


RR Commercial ESCCommercial ESC


RR Mirror TimeMirror Time

There are times when hour and minutereadings are same, such as 1:01, 2:02, 3:03,etc. What is the shortest possible timebetween two different readings of this mirrortime?

49min, 12:12 1:01


RR Who is lying?Who is lying?

Four friends Andrew, Barbara, Cindy, andDaniel were shown a number. Here is whatthey had to say about that number:

Andrew: It has two digits

Barbara: It goes evenly into 150

Cindy: It is not 150

Daniel: It is divisible by 25

It turns out that one and only one of the fourfriends is lying. Which one is it?

D


RR Stepper MotorsStepper Motors

A motor produces rotation through equalangles, the so-called steps, for each digitalpulse supplied to its input.

NS

N S

N

S

N

S


RR Obtain Smaller StepsObtain Smaller Steps

A stepper motor with 4 teeth rotor and 6 teeth stator willobtain minimum step of 15

(A)

1

23

4

5 6

a

b

c

d

(C)

1

23

4

5 6

ab

cd

(B)

1

23

4

5 6

a

b

c

d

Develop a control scheme for a stepper motor with 8teeth rotor and 6 teeth stator

Given a 50 teeth rotor and 40 teeth stator, what isthe minimum step?


RR MicroMicro--SteppingStepping

In micro- stepping, the

power- on or power- off for each coil is donegradually by dividingthe changes intosmaller divisions.

N

S

N

S

N

S

Half stepping

Pro and Cons.

Smaller stepping angles

Smoother rotation

Complex controller

Develop half stepping scheme for the previous 4/6 example


11/13


RR Servo MotorServo Motor

A servomotor is any motor with feedback that canbe controlled to move at a desired speed (andconsequently, torque), for a desired angle ofrotation.

MotorDynamics Load

Differentiate

Feedback

Desiredposition &velocity +

_Position

Velocity

Error


RR Anatomy of a Servo MotorAnatomy of a Servo Motor


RR Angle ControlAngle Control


RR Digital Control of a MotorDigital Control of a Motor

The speed of the motor is controlled byvarying voltage

Control signal from computer is digital, henceneed conduct digital-to-analog converters(DAC)

The resolution of the control is determined bythe number of ports or bits (2n)


RR Servo Motor ControllerServo Motor Controller

PIC16C73 based

SV203 Servo

Motor Controller

PRINT #1,"BD";ID$;"SV";Servo$;"M";Position$


RR Pulse Width Modulation (PWM)Pulse Width Modulation (PWM)

The voltage is sent as pulse with constant voltage

The average voltage is determined by the width ofthe pulse

Time

V

tT

Vcc

Vout

T

tVV ccout

=

T 4T3T2T 5T0


12/13


RR Industrial AC MotorIndustrial AC Motor

1000 HP1 HP


RR AC Induction MotorAC Induction Motor

Same theory of DC motor to turn the rotor

No wiring required for rotor

3-phase AC to induct rotating electro-

magnetic field.


RR Component of an AC MotorComponent of an AC Motor

Stator Rotor


RR 3 Phase Alternating Current (AC)3 Phase Alternating Current (AC)


RR 3 Phase AC Wiring3 Phase AC Wiring

iA

iC

iBD2

D1

D3

D5D4

D6

Y (Star) wiring

(Triangle) wiring


RR

D3

D6

D1

D4

D5

D2

iA D1

iC

iBD2

D3

D5 D4

D6

iA

iB

iC

V

t

0

t1 t2 t3 t4 t5 t6

t= 0x

x

N

S


13/13


RR Turning ElectroTurning Electro--Magnetic FieldMagnetic Field

D3

D6

D1

D4

D5

D2

iA D1

iC

iBD2

D3

D5 D4

D6

iA iBiCV

t

0

t1 t2 t3 t4 t5 t6

t= t1, t2,?

???


RR

D3

D6

D1

D4

D5

D2

x

x

x

D3

D6

D1

D4

D5

D2

x

x

t= t1t= t2

t= t3

t= t4

D3

D6

D1

D4

D5

D2x

x

x

D3

D6

D1

D4

D5

D2

x

x

x

D3

D6

D1

D4

D5

D2x

x

x

t= t5 t= t6

D3

D6

D1

D4

D5

D2x

x

x


RR Use of Reduction GearsUse of Reduction Gears

In most motor powered system, we use reductiongears or other mechanics to reduce speed andincrease torque.

Inertia of loadIl, Inertia of motorIm, Gear ratio N,viscous friction of load and motor are IlandIm

Motor

Gears

Loadm& L

&

Tm


RR Dynamic EquationsDynamic Equations

mNl && 1= mNl

&&&& 1=and

lN

m

l TT1=

mlNmmlNm

llllNmmmm

lNmmmmm

bbII

bIbI

TbIT

&&&

&&&&&&

&&&

)()(

)(

22

11

1

1

+++=

+++=

++=

Total inertia Total friction


RR ExerciseExercise

A motor withIm=0.015 kgm2 and maximum torque of 8Nm is

connected to a uniformly distributed arm with aconcentrated mass at its end. Ignoring the inertia felt by themotor and viscous friction in the system, calculate the totalinertia felt by the motor and the maximum angularacceleration it can develop if the gear ratio is (a) N=3 and(b) N=30.

Motor

m& L

&

0.5m

3kg

2kg

actuators (1)

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